Mixed Zone Research Articles

A salinity cut-off method to control numerical dispersion in low-salinity waterflooding simulation

Low-salinity or controlled salinity waterflooding (LSWF) is a promising enhanced oil recovery (EOR) technique. In simulations of this process, numerical dispersion smears saturation fronts, causing errors in the results. The objective of this work is to control these effects in LSWF simulation. We examine the impact of numerical dispersion on simulated LSWF performance. The low-salinity (LS) front is smeared even at unfeasibly fine grids. The velocities of the water fronts are altered. A numerical mixed zone forms around the interface between the injected and resident brines. This mimics a typical physical mixing effect.In reservoir simulation, threshold salinities are defined where the low salinity effect (LSE) is first encountered. It has been suggested that numerical dispersion effects can be corrected by imposing effective thresholds. We demonstrate that existing methods to evaluate these effective salinities do not accurately predict the salt front movement especially when dispersion is significant.We propose a simple simulation-based approach to evaluate the effective salinities based on the conservation of volumes of the resident and injected brines in the reference and upscaled solutions. After comparing analytical and corrected coarse-grid solutions in one-dimension, the effectiveness of the approach is demonstrated in multi-dimensional systems.A method is proposed to control the numerical mixed zone to replicate a physical longitudinal mixing effect. This method is demonstrated in one-dimension and does not require a fine-grid numerical solution as a benchmark. We investigate the effects of effective thresholds on the modeled transverse mixing or dispersion. A method to model transverse dispersion in simulations with an effective longitudinal component is suggested. This method is extended to the explicit modeling of physical dispersion in systems with transverse flows.We can now simply evaluate the effective salinities for a simulation grid; and control its numerical dispersion effects to representative physical mixing or dispersion.

Complex mineralogical-geochemical sequences and weathering events in the supergene ore of the Cu–Co Luiswishi deposit (Katanga, D.R. Congo)

The Luiswishi Cu–Co ore deposit (Haut-Katanga, D.R. Congo) belongs to the Katanga Copperbelt (KCB), a world-class Cu–Co district. The primary orebodies in the KCB consist of sulphide ore hosted in Neoproterozoic fine-grained siliciclastic and carbonate sedimentary rocks. The secondary weathered ores are still poorly documented, though most of them are strongly enriched in both copper and cobalt with regard to the primary sulphide ores. Combined mineralogical (transmitted and reflected light microscopy, XRD, SEM-EDX) and geochemical investigations (FUS-MS and FUS-ICP) on both host rocks and ore minerals allow identifying and characterizing three distinct zones in the studied profile, at Luiswishi, from base to top: the protore, which contains sulphides and massive dolomite; the cementation zone where oxides and sulphides coexist, and the saprolite, comprised of oxidized ores only. The mixed oxidized-sulphide zone occurs down to about 100 m in depth. At Luiswishi, the formation of the oxidized ores proceeded as follows: (1) oxidation of the primary sulphides (mainly chalcopyrite, carrollite and pyrite); (2) rapid neutralization of the released acidity by carbonate minerals (mainly dolomite) and Mg-chlorite in the host rock; and (3) concomitant precipitation of a wide range of oxidized mineral phases: goethite, malachite, heterogenite, pseudomalachite, amorphous copper silicate compound. Complex geometries and recurring mineralogical successions within heterogenite – malachite, or malachite – copper silicate – malachite aggregates are highlighted in the weathering profile. Mineralogical transformations in the weathered profile result in an overall selective leaching of the LREE and a concomitant residual enrichment in HREE. The leached LREE accumulate in the cementation zone, where both secondary chalcocite-type sulphides and residual and replacement goethite form, by oxidation within the rims and cracks in chalcopyrite. Deriving from a specific protore, the oxidized S.D.1b (formerly “Black Ore Mineralized Zone” or B.O.M.Z.) shows a specific geochemical response to weathering, with enrichment in both LREE and HREE and positive Ce-anomaly in the saprolite.

Shock-wave experiment with the Chelyabinsk LL5 meteorite: experimental parameters and the texture of the shock-affected material)

The shock experiment with Chelyabinsk LL5 light lithology material was performed as a spherical geometry shock. The material experienced shock and thermal metamorphism from the initial S3–4 up to complete melt stage. Temperature and pressure realized were estimated above 2000°С and 90 GPa. Textural shock effects were studied by the means of optical and electron microscopy. By the only experimental impact, all the range of the shock pressures and temperatures was realized. Four zones were revealed from the petrographic analysis: 1 – melt zone, 2 – melted silicates zone, 3 – black ring zone, 4 – weakly shocked initial material. Several features of the material texture were noted: displacement of the metal and troilite phases from the central melt zone; mixed lithology zone formation (light-colored chondrules within the silicate melt); dark-colored lithology ring formation; generation of radial-oriented shock veins. Thus, at the experimental fragment, four texture zones were formed. These zones correspond to the different lithology types of the Chelyabinsk LL5 meteorite, which could be found in different fragments of the meteoritic shower from UrFU collection. The results obtained prove that the shock wave loading experiment could be used for space shock modeling. Therefore, the processes of the small bodies of the Solar system could be experimentally modeled at the laboratory conditions.

Effect of APS flash bond coatings and curvature on TBC performance on rod specimens

The addition of an air plasma sprayed (APS) “flash” bond coating layer on top of a high velocity oxy-fuel (HVOF) bond coating significantly extended the lifetime of APS yttria stabilized zirconia (YSZ) thermal barrier coatings (TBC) on rod specimens of superalloy 247 tested using 100-h cycles in air+10%H2O at 1100 °C. The flash bond coatings of both NiCoCrAlY and NiCoCrAlYHfSi powder were compared to an HVOF-only and a vacuum plasma sprayed (VPS) NiCoCrAlYHfSi bond coating. The flash coatings appear to form a mixed oxide-metal zone, which likely inhibits crack formation and therefore extends lifetime compared to conventional bond coatings. The underlying dense HVOF layer appeared to act as a source of Al for this intermixed zone and prevented the oxide from penetrating deeper into the bond coating. Residual stress in the thermally-grown Al2O3 scale was measured using photo-luminescence piezospectroscopy (PLPS) as a function of time for each coating variation, including a comparison of concave and convex surfaces on a specially designed rod.

Recycled Stone/ABS particulate composite: Micromechanical finite element fracture analysis

New stone composite samples, fabricated using nano- to micro-sized recycled granite particles with irregular shapes and random distribution within a ABS matrix, demonstrate a highly nonlinear and complex fracture behavior. To model this behavior, a mixed mode cohesive zone finite element model is identified using the single-leg bending (SLB), in order to represent the granite particles-ABS interfacial debonding. An inverse methodology is then proposed to determine the parameters of the cohesive zone (CZM). A direct method based on J-integral approach is employed to determine the effective parameters of the traction-separation law. A two dimensional micromechanical extended finite element model (XFEM) of the composite is generated using X-ray micro-computed tomography (XMT) to mimic the actual shape of the particles. Finally, the identified cohesive model parameters have been employed to simulate the crack growth within the granite particulates/ABS composite. The comparison of the numerical and experimental results of the SLB test demonstrated the effectiveness of the proposed simulation framework.

The effect of spruce plantation density on resilience of mixed forests in the Perm Krai

Over the course of the last few decades, many countries across the globe have experienced mass desiccation of spruce plantations. The subject of our research was the spruce forests of the Russian Perm Krai’s mixed forest zone. Spruce is a shade–tolerant tree species and low plantation density may adversely affect the spruce health. The aim of this research is to establish how influential the spruce stand density is on causing desiccation in mixed zones in the Perm Krai. The results of an on-site survey which had recorded spruce desiccation in 2017 were analysed. Within the boundaries of the aforementioned forest areas, 2017 saw the desiccation of spruce trees in 301 forest allotments covering an area of 5,343.7 ha. The value of the weighted average category of spruce forest health in Prikamye varies from 2.7 (severely weakened) to 4.2 (desiccating), and the percentage of the volume of spruce deadwood varies from 17% to 59.5%. When the spruce stand density rises from 0.4 to 0.8, spruce stand resilience to desiccation increases.

Gorgonian octocoral community at Varadero coral reef in the Colombian Caribbean: diversity and spatial distribution

Varadero reef has unique ecological characteristics and faces the risk of disappearing because of the dredging for an access channel of large vessels to the Cartagena port in Colombia. In this ecosystem, the sessile benthic community, such as gorgonian octocorals and associated fauna, will be impacted. We examined the diversity and spatial distribution of gorgonians from seven sites located in the mixed coral reef zone. These organisms are generally found in depths between 6 and 10 m in the area. The richness of the gorgoniansspecies is lower than that recorded in other areas of the Caribbean. The low values of abundance and richness species are due to the characteristics of reef setoff and sedimentation processes existing in Cartagena bay.

Effect of Non-Ideal Mixing on Heat Transfer of non-Newtonian Liquids in a Mechanically Agitated Vessel

Abstract Effect of non-ideal mixing on heat transfer phenomena is studied in an anchor agitated vessel processed with viscous Newtonian and non-Newtonian fluids. Influence of critical variables such as rotational speed and properties of the fluid on heat transfer coefficient and heat transfer area has been investigated. Based on the flow pattern generated by an anchor agitator, a multi parameter model for quantifying the extent of non-ideality is developed and the parameters of the model, fraction of well mixed zone and the exchange flow rate are evaluated on the basis of tracer response data. Heat transfer experiments are also conducted under unsteady state conditions using same agitated vessel under similar operating conditions using Castor oil, Castor oil methyl esters (CME) and carboxy methyl cellulose (CMC 0.5 %, 1 %), soap solution as process fluids. Based on the results obtained from this analysis, a commercial scale reactor of a capacity of 20 Kl for saponification of hydrogenated castor oil has been designed using different scaleup rules. Power per unit volume found to give desirable results as it gives acceptable values for heat transfer coefficient and power consumption. Equal power per unit volume gives good mixing and high heat transfer coefficient with slightly higher power consumption and the error involved in heat transfer area calculation is small giving optimum cost of the experimental unit.

In situ weathering of rocks or aeolian silt deposition: key parameters for verifying parent material and pedogenesis in the Opawskie Mountains\u2014a case study from SW Poland

PurposeThe aims: (1) to investigate the role of the in situ weathering of bedrock in providing substrate for soil formation; (2) to evaluate the aeolian contribution to the mountainous soils in the vicinity of thick loess cover; and (3) to determine the influence of aeolian silt on further soil development.Materials and methodsThe sampled sites were arranged along the slope toposequence, where an aeolian/silt admixture possibly occurred. Each soil catena started at the top of a hill and ended at its foot. Such an arrangement of the soil profiles ensured the tracking of loess thickness variations and detection of the depth of the residuum-derived materials. One reference soil profile, consisting of aeolian silt deposits, was made. The following soil properties were determined: pH, organic carbon content, soil texture, exchangeable acidity, exchangeable ions and geochemistry. In addition, thin sections were prepared from rock samples to confirm the type of bedrock present.Results and discussionThe soils in the studied area were classified as Cambisols, Luvisols and Stagnosols, characterised by silt loam texture and a high content of elements indicating an aeolian silt contribution—Hf (7.4 to 14.8 ppm) and Zr (274.4 to 549.0 ppm). These values differ strongly from the residues typical of weathered quartzite, greywacke or catalasite substrates, which generally have low concentrations of Hf and Zr (0.7 to 7.0 ppm and 26.0 to 263 ppm, respectively). Based on the morphological, textural and geochemical data of the studied soils, three layers were distinguished, which show different inputs of aeolian silt: (1) an aeolian silt mantle; (2) a mixed zone in which loess was incorporated into the local material; and (3) a basal zone, free of the influence of aeolian silt. Based on the obtained results, a hypothetical pathway for soil formation in mountainous areas, influenced by aeolian silt admixing, was proposed.ConclusionsOur study demonstrates that the soils developed in the Opawskie Mountains are characterised by an aeolian silt influence. This differentiates them from weakly developed soils, which comprise materials formed during in situ weathering only. Materials originating from bedrock weathering did not play an independent role as the parent material for the studied pedons. Aeolian silt was admixed with already existing autochthonous substrates, or completely replaced them. This influence on the soil formation resulted in the occurrence of Luvisols, Stagnosols and Cambisols. Such soils cannot be formed from the weathering of quartzites and greywackes, which contribute to a less structure-forming medium.

Magma chamber processes and geodynamic implications of the Pithora pluton, Bastar Craton, Central India

The interaction between the coeval mafic and felsic magmas result in mixing, mingling, and chemical exchanges between both the end‐member magmas. We document the features relevant to the magma chamber processes and quantify the extent of mixing by means of detailed field, petrographic, mineral, and whole‐rock geochemistry from one of the less known granitic plutons from the Pithora region that forms part of the Kanker granite, Bastar Craton. The study area is composed of granite, granodiorite (mixed zone), and quartz diorite microgranular enclaves (MEs). The occurrence of syn‐plutonic mafic dykes, cuspate contact, magmatic flow textures, and hybridization suggest the coeval emplacement of end‐member magmas. Petrographic evidence such as disequilibrium textures such as resorption, quartz ocelli, and spikes in plagioclase, acicular apatites, and mafic clots are formed by magma mixing. Plagioclase from MEs and the mixed region exhibit disequilibrium textures such as normal, reverse, and oscillatory zoning suggestive of magma mixing. Whole‐rock geochemical data indicates the metaluminous to peraluminous host granites and metaluminous ME. The broadly linear trend of geochemical variation diagrams for these granitoids and MEs showcase the hybridization of two end‐member magmas. The mineral chemistry of the biotites and hornblende show subduction affinity, being further constrained by whole‐rock trace elemental systematics. The granitoids of Pithora region were formed in a subduction setting where large‐scale mantle‐ and crustal‐derived magmas were generated and subsequently mixed at crustal emplacement level.

Prokaryote Communities at Active Chimney andIn SituColonization Devices After a Magmatic Degassing Event (37°N MAR, EMSO‐Azores Deep‐Sea Observatory)

AbstractThe mixing zone between high‐temperature hydrothermal fluids and seawater produces redox gradients, promoting the development of unique ecosystems based on chemotrophy. The structure of microbial communities depends on their environment, which can vary according to space and time. Hydrothermal circulation within the oceanic crust determines the chemical composition and flow of fluids, depending on underground events (earthquakes, volcanic episodes, etc.) and impacts the development of microbial communities. This link between hydrothermal vent communities and deep geological events is the focus of the present study, the first of its kind for slow‐spreading ridge. In this study, we present a unique set of multidisciplinary data collected from 2008 to 2011 on the Eiffel Tower hydrothermal site (Lucky Strike vent field, Mid‐Atlantic Ridge, MAR). We benefit from continuous geophysical monitoring (temperature and seismicity) of the site, annual sampling of hydrothermal fluids (hot and diffuse) for geochemistry analyses, sampling of hydrothermal chimneys, and an in situ microbial colonization experiment over a year for microbial study. The high CO2content and concentrations of major elements (Cl, Ca, and Si) and SO4in the end‐member fluids collected in 2010 indicate that a magmatic degassing occurred between 2009 and 2010 under the Lucky Strike hydrothermal field. This is supported by the large temperature variations observed in March–April 2010. These magmatic CO2inputs seem to have affected microbial communities colonizing the high‐temperature chimney, as well as the basalts in the more diffuse and mixed zone, promoting the development of thermophilic/anaerobicArchaeaandBacteria(Archaeoglobales, Nautiliales, and Nitratiruptoraceae).

Changes of vegetation in southern China

In order to reveal the changes of vegetation in southern China since the Last Glacial Maximum, we have established high-resolution time scales and palynological sequences of borehole profiles by drilling cores in some weak areas of the research to restore vegetation changes over the past 20,000 years on the basis of previous work. This paper gives the vegetation zoning maps of 18, 9 and 6 ka BP respectively in southern China, and describes the distribution characteristics of plants in different zones/subzones. The results show that the vegetation zonations around 18 ka BP were significantly different from that at present. It appeared in turn with Cold-temperate coniferous forest and alpine meadow steppe zone, and Temperate mixed coniferous and broad-leaved forest zone/warm temperate deciduous broad-leaved forest zone from northwest to southeast in the west, and Temperate mixed coniferous and broad-leaved forest zone, Warm temperate deciduous broad-leaved forest zone, and Northern subtropical mixed evergreen and deciduous broad-leaved forest zone from north to south in the central and east. The vegetation distribution around 9 ka BP changed distinctively. Except that the northwest part was located in Mountain temperate mixed coniferous and broad-leaved forest zone, the vegetation in other areas occurred in turn with North subtropical mixed evergreen and deciduous broad-leaved forest subzone, Mid-subtropical typical evergreen broad-leaved forest subzone, and South subtropical monsoon evergreen broad-leaved forest subzone/Tropical seasonal rainforest and rainforest zone from north to south. There was little change in the appearance of vegetation zonations between 6 and 9 ka BP, but the northern edge of each vegetation belt moved a little northward, reflecting that the overall climate became warmer around 6 ka BP. The vegetation changes in southern China over the past 20,000 years were largely driven by environmental changes. Climate change was the main factor affecting the vegetation distribution. The impact of human activities became more and more remarkable in the later period. In the lower reaches of the Yangtze River and the delta region, sea level changes also influenced the vegetation distribution.

Functionally Graded SS 316L to Ni-Based Structures Produced by 3D Plasma Metal Deposition

In this investigation, the fabrication of functionally graded structures of SS316L to Ni-based alloys were studied, using the novel technique 3D plasma metal deposition. Two Ni-based alloys were used, a heat resistance alloy Ni80-20 and the solid-solution strengthened Ni625. Different configurations were analyzed, for the Ni80-20 a hard transition and a smooth transition with a region of 50% SS316L/50% Ni80-20. Regarding the structures with Ni625, a smooth transition configuration and variations in the heat input were applied. The effect of the process parameters on the geometry of the structures and the microstructures was studied. Microstructure examinations were carried out using optical and scanning electron microscopy. In addition, microhardness analysis were made on the interfaces. In general, the smooth transition of both systems showed a gradual change in the properties. The microstructural results for the SS316L (both systems) showed an austenite matrix with δ-phase. For the mixed zone and the Ni80-20 an austenite (γ) matrix with some M7C3 precipitates and laves phase were recognized. The as-built Ni625 microstructure was composed of an austenite (γ) matrix with secondary phases laves and δ-Ni3Nb, and precipitates M7C3. The mixed zone exhibited the same phases but with changes in the morphology.

An effective variant ring signature-based pseudonym changing mechanism for privacy preservation in mixed zones of vehicular networks

The privacy information related to the location of the vehicles need to be concealed with utmost care in the vehicular network since its disclosure leads to a diversified number of attacks that degrades the performance of the network. But, the privacy of vehicles relies on a kind of pseudonym changing mechanism utilized in the mix zone of the vehicular networks. However, the strength of location privacy is influenced by the lower vehicular density and characteristics of decentralization in the mixed zone. In this paper, an effective variant ring signature-based pseudonym changing mechanism (EVRS-PCM) is contributed for privacy preservation under decentralization and reduced density of vehicles. This proposed EVRS-PCM approach uses a ring signature-based pseudonym changing procedure that potentially minimizes the number of pseudonyms notifications under the formation of mixed zones in the network for facilitating excellent location privacy. The results of the proposed EVRS-PCM approach confirmed an optimal rate of success rate, location privacy and the percentage decrease in the number of pseudonym notifications under the varying proportion of mixed zones, distances and vehicles in the network.

The problem of drying up spruce stands and ways to solve it

The last decades has been witnessed of the mass spruce stands drying up problem in different countries of the world. The investigation purpose consists in establishing influence of the growth conditions and the bark beetle, on the drying up of spruce forests. Forest stands of the coniferous-broadleaved (mixed) zone forests in Russian Federation served as an object of our researcb. Based on the results of the acts of pathologic inspection, it is established that the share of drying up spruce forests decreases with increasing soil fertility and moisture. The influence of the bark beetle was investigated on the basis of materials of three sample plots in stands of the green-moss spruce type of forest. We did not find traces of vital activities of the bark beetle by the drying spruce trees with a diameter at altitudes of 1.3 m to 14 cm fully, as well as with a diameter of 14 to 22 cm partly. The fact revealed is explained by the fact that these spruce trees have a thin bark which is not enough for the beetle laying inside of it the mother gallery, and the brood bark for subsequent feeding. The bark beetle is not the primary reason of the spruce forests drying in the Permsky Kray. It is necessary to conduct a much deeper study on this problem.

Failure mechanisms in carbon fiber reinforced plastics (CFRP) / aluminum (Al) adhesive bonds subjected to low-velocity transverse pre-impact following by axial post-tension

The present study aimed to explore the effects of impact surface and impact energy on the residual characteristics of the carbon fiber reinforced plastics (CFRP)/aluminum (Al) adhesive bonded joints. The adhesive specimens were manufactured in the hot pressing machine with specific curing temperature and curing pressure of the adhesive. In the experiments, a transverse low velocity pre-impact was carried out first and then followed by the axial (longitudinal) tensile test. The results divulged that CFRP, as an impact surface, could generate better structural integrity and decrease loss of joint strength in comparison with the aluminum impact surface. The mechanism for alternating residual tensile strength resulting from transverse impact load was the combined effect of both damage and mechanical interlocking effectiveness. The residual tensile strength and failure displacement decreased with increasing impact energy except for the joint strength impacted onto the aluminum surface at 10 J due to the prominent mechanical interlocking effect. The strain evolution paths in the adherends at the overlap region presented the different forms when impacted onto the different surfaces. In the tensile tests, the fracture surfaces for the joints with impacting on the aluminum surface can be classified as shear failure zone, annular failure zone and mixed failure zone, while the fracture surfaces for the joints with impacting onto the CFRP surface classified to be shear failure zone and crossed impact zone. This study is expected to provide systematic understanding on crashing behavior of adhesive joints with dissimilar materials for multiple impacts from different directions.

Assessment of contemporary erosion/sedimentation rates trend within a small cultivated catchment using the radiocaesium-137 as a chronomarker (a case study from the Udmurt republic, European Russia)

This paper is devoted to revealing and estimating the contemporary soil erosion rates trend within arable lands in the south of the forest zone of European Russia, based on the study of sedimentation rates at a small dry valley bottom with almost completely cultivated catchment slopes. The dry valley catchment (0.68 km2) is located in the south part of the Udmurt Republic (the mixed forests zone) within the Izh River basin. The bomb-derived and Chernobyl-derived radiocaesium–137 was used for dating valley bottom sediments in two time intervals: 1954(1963)–1986 and 1986–2016. To analyze the causes of change in sediment redistribution rates, morphological and morphometric analyzes of the valley, the results of year-to-year observations for gully heads retreat in the catchment vicinities, hydrometeorological observations of the Russian Hydrometeorological Survey network, and also aero- and satellite images across years were used. There was a noticeable decrease in the sedimentation rates of washed-out soil material from the catchment slopes at the valley bottom over the past 60 years: from 1.8–2.5 cm/year during 1954–1986 to 0.15–0.75 cm/year for 1986–2016. Hence, the sedimentation rates have decreased by 2.5–3 times as a minimum. This trend is consistent with a decline of the average retreat rates of gully headcuts within cultivated lands in the Udmurt Republic over the past 40 years — from 1.3 m/year in 1978–1997 to 0.3 m/year in 1998–2014. We suppose that the main reason for such significant reduction of erosion rates was a increase in protective crop coefficient associated with a increase in the proportion of perennial grasses since the late 1980s. Additional contribution to the erosion reduction was owing to a decrease in surface snowmelt water runoff within the catchment area since the early 2000s, associated with the reduction in soil freezing depth and general increase in air temperature during the winter and spring months in this region of the Russian Plain.

Metallurgical and mechanical investigations of Inconel 625 overlay welds produced by GMAW-hardfacing process on AISI 347 pipes

Inconel 625 is a widely employed material for hardfacing to protect components of aircrafts, oil refinery and power generation, possessing better corrosion resistance behaviour at high temperature applications. These characteristics are related with the hardfacing material composition and microstructure of overlaid welds which is influenced by the process parameters and the substrate composition of the component to be protected. Hardfacing has been extensively used for modifying surface and repairing. In this research, single bead overlays of Inconel 625 were deposited on the surface of AISI 347 pipe by GMAW process. Overlaid welds were deposited at three different heat inputs (0.48 kJ/mm, 0.53 kJ/mm and 0.59 kJ/mm) to synergic mode, while the voltage and wire feed rate are pre-programmed. The overlaid weld thickness varied from 1.5 mm to 2.62 mm on substrate with suitable overlaying parameters. This study was explored with Optical microscopy, Energy-dispersive x-ray spectroscopy (EDS), scanning electron microscopy (SEM), and mechanical tests were used for microstructural and mechanical characterization. The results showed that the overlay welds of Inconel 625 exemplified a noticeable microstructure upon solidification, while the bond interface can be observed and divided into distinct zones. Near the bonding interface, a non-mixed zone with precipitated ferrite of different formations were observed. The surface of overlaid weld microstructure to interface of substrate/weld overlay comprised of cellular, columnar and fine dendrites. An increase in Fe wt% in the partially mixed zone is corroborated to the melting and dispersion of the substrate. Uni-axial tension test and Vickers-micro hardness test were carried out on the specimen sectioned from overlay welds. The mechanical test responses revealed that the tensile strength and micro-hardness of the overlaid welds improved significantly compared to substrate. The mechanical properties of hardfaced area were better than bonding area and superior to substrate, revealing an excellent overlay weld deposition using Inconel 625.

Characterization on the gradient microstructure near the fusion interface of dissimilar metal between high Cr heat-resistant steel and Ni-based Alloy 617

The gradient microstructure occurring adjacent to fusion interface of dissimilar metal between high Cr steel and nickel-based Alloy 617 was characterized in detail, and its formation mechanism was discussed in this paper. The island-like and peninsula-like structures present various characters due to difference in elements mixing during welding process. It is found that an unmixed zone (UMZ), a partial mixed zone (PMZ) with lamellar structure and a transition zone (TZ) together make up island-like gradient microstructures. In UMZ, the tempered martensite with much finer equiaxed grains was the main microstructure. In PMZ, nickel-deficient ferrite as the dendritic core, which is separated by nickel-rich fresh lath martensite in interdendritic region, lead to the lamellar structure. The formation of fresh martensite showed phase transition happened under post weld heat treatment (PWHT), which is also verified by the higher nanohardness. In TZ, the occurrence of carbide-free ferrite indicates the carbon diffusion was inhibited by the reaustenitization of TZ. It is also found that the formation of gradient microstructure has close relationship with the angle (θ) between tangents of fusion line and the interface of multi-layer, it is easier to form gradient microstructure as θ > 0 due to complex fluid flow of steel. So, suitable design of multi-layer in weld could help in controlling the formation of this kind of gradient microstructure.

Fine detection technology of gas outburst area based on direct current method in Zhuxianzhuang Coal Mine, China

In this study, with No. II 1051 working face of Zhuxianzhuang Coal Mine taken as the research object, the electric characteristics of coal samples were tested in the laboratory, and the resistivity imaging was carried out on the working surface via direct current (DC) prospecting instrument on site. Then, fine division was performed on outburst danger areas through gas geological analysis. Finally, mining verification and analysis were conducted. The results suggest that the variation laws of electrical characteristics of samples obtained in the laboratory test correspond well to those gained through site detection. Resistance does not distribute homogeneously in the working face, demonstrating regional significant high and low resistance, which is jointly induced by gas, stress, structure and water. Based on the aforesaid analyses, five outburst areas are determined, including high- and low-resistance regions and the mixed zone. The analysis results of gas occurrence regularity agree with the on-site situation, proving that the result of DC prospecting can reflect the distribution of outburst danger areas. The finding is of great importance for realizing fine detection of gas outburst.